Classifications

• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B1/00—Constructional features of ropes or cables
  • D07B1/06—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core
  • D07B1/0606—Reinforcing cords for rubber or plastic articles
  • D07B1/0613—Reinforcing cords for rubber or plastic articles the reinforcing cords being characterised by the rope configuration
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  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B1/00—Constructional features of ropes or cables
  • D07B1/06—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
  • B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
• • D—TEXTILES; PAPER
  • D02—YARNS; MECHANICAL FINISHING OF YARNS OR ROPES; WARPING OR BEAMING
  • D02G—CRIMPING OR CURLING FIBRES, FILAMENTS, THREADS, OR YARNS; YARNS OR THREADS
  • D02G3/00—Yarns or threads, e.g. fancy yarns; Processes or apparatus for the production thereof, not otherwise provided for
  • D02G3/02—Yarns or threads characterised by the material or by the materials from which they are made
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B1/00—Constructional features of ropes or cables
  • D07B1/06—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core
  • D07B1/0606—Reinforcing cords for rubber or plastic articles
  • D07B1/062—Reinforcing cords for rubber or plastic articles the reinforcing cords being characterised by the strand configuration
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B1/00—Constructional features of ropes or cables
  • D07B1/06—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core
  • D07B1/0606—Reinforcing cords for rubber or plastic articles
  • D07B1/062—Reinforcing cords for rubber or plastic articles the reinforcing cords being characterised by the strand configuration
  • D07B1/0626—Reinforcing cords for rubber or plastic articles the reinforcing cords being characterised by the strand configuration the reinforcing cords consisting of three core wires or filaments and at least one layer of outer wires or filaments, i.e. a 3+N configuration
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B1/00—Constructional features of ropes or cables
  • D07B1/16—Ropes or cables with an enveloping sheathing or inlays of rubber or plastics
  • D07B1/165—Ropes or cables with an enveloping sheathing or inlays of rubber or plastics characterised by a plastic or rubber inlay
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/10—Rope or cable structures
  • D07B2201/1028—Rope or cable structures characterised by the number of strands
  • D07B2201/1032—Rope or cable structures characterised by the number of strands three to eight strands respectively forming a single layer
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/10—Rope or cable structures
  • D07B2201/104—Rope or cable structures twisted
  • D07B2201/1064—Rope or cable structures twisted characterised by lay direction of the strand compared to the lay direction of the wires in the strand
  • D07B2201/1068—Rope or cable structures twisted characterised by lay direction of the strand compared to the lay direction of the wires in the strand having the same lay direction
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2001—Wires or filaments
  • D07B2201/2006—Wires or filaments characterised by a value or range of the dimension given
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2001—Wires or filaments
  • D07B2201/201—Wires or filaments characterised by a coating
  • D07B2201/2011—Wires or filaments characterised by a coating comprising metals
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2015—Strands
  • D07B2201/2023—Strands with core
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2015—Strands
  • D07B2201/2024—Strands twisted
  • D07B2201/2029—Open winding
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2015—Strands
  • D07B2201/2024—Strands twisted
  • D07B2201/2029—Open winding
  • D07B2201/2031—Different twist pitch
  • D07B2201/2032—Different twist pitch compared with the core
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2015—Strands
  • D07B2201/2036—Strands characterised by the use of different wires or filaments
  • D07B2201/2037—Strands characterised by the use of different wires or filaments regarding the dimension of the wires or filaments
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2015—Strands
  • D07B2201/2038—Strands characterised by the number of wires or filaments
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2015—Strands
  • D07B2201/2046—Strands comprising fillers
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2047—Cores
  • D07B2201/2052—Cores characterised by their structure
  • D07B2201/2059—Cores characterised by their structure comprising wires
  • D07B2201/2061—Cores characterised by their structure comprising wires resulting in a twisted structure
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2047—Cores
  • D07B2201/2052—Cores characterised by their structure
  • D07B2201/2059—Cores characterised by their structure comprising wires
  • D07B2201/2062—Cores characterised by their structure comprising wires comprising fillers
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2075—Fillers
  • D07B2201/2077—Fillers having an anti-corrosive function
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2075—Fillers
  • D07B2201/2079—Fillers characterised by the kind or amount of filling
  • D07B2201/2081—Fillers characterised by the kind or amount of filling having maximum filling
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2201/00—Ropes or cables
  • D07B2201/20—Rope or cable components
  • D07B2201/2075—Fillers
  • D07B2201/2082—Fillers characterised by the materials used
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2205/00—Rope or cable materials
  • D07B2205/30—Inorganic materials
  • D07B2205/3021—Metals
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2205/00—Rope or cable materials
  • D07B2205/30—Inorganic materials
  • D07B2205/3021—Metals
  • D07B2205/306—Aluminium (Al)
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2205/00—Rope or cable materials
  • D07B2205/30—Inorganic materials
  • D07B2205/3021—Metals
  • D07B2205/3071—Zinc (Zn)
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2205/00—Rope or cable materials
  • D07B2205/30—Inorganic materials
  • D07B2205/3021—Metals
  • D07B2205/3085—Alloys, i.e. non ferrous
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2205/00—Rope or cable materials
  • D07B2205/30—Inorganic materials
  • D07B2205/3021—Metals
  • D07B2205/3085—Alloys, i.e. non ferrous
  • D07B2205/3089—Brass, i.e. copper (Cu) and zinc (Zn) alloys
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2401/00—Aspects related to the problem to be solved or advantage
  • D07B2401/20—Aspects related to the problem to be solved or advantage related to ropes or cables
  • D07B2401/2005—Elongation or elasticity
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2401/00—Aspects related to the problem to be solved or advantage
  • D07B2401/20—Aspects related to the problem to be solved or advantage related to ropes or cables
  • D07B2401/208—Enabling filler penetration
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2501/00—Application field
  • D07B2501/20—Application field related to ropes or cables
  • D07B2501/2046—Tire cords
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B2501/00—Application field
  • D07B2501/20—Application field related to ropes or cables
  • D07B2501/2076—Power transmissions
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B5/00—Making ropes or cables from special materials or of particular form
  • D07B5/12—Making ropes or cables from special materials or of particular form of low twist or low tension by processes comprising setting or straightening treatments
• • D—TEXTILES; PAPER
  • D07—ROPES; CABLES OTHER THAN ELECTRIC
  • D07B—ROPES OR CABLES IN GENERAL
  • D07B7/00—Details of, or auxiliary devices incorporated in, rope- or cable-making machines; Auxiliary apparatus associated with such machines
  • D07B7/02—Machine details; Auxiliary devices
  • D07B7/14—Machine details; Auxiliary devices for coating or wrapping ropes, cables, or component strands thereof
  • D07B7/145—Coating or filling-up interstices

Definitions

• the present invention relates to high-strength multistrand cables, which can especially be used for the reinforcement of pneumatic tyres for heavy industrial vehicles, such as heavy goods vehicles or civil engineering vehicles.
• the invention also relates to tyres and to the reinforcements for tyres, and in particular to the crown reinforcements, also called “belts", of tyres, and more particularly the reinforcement of the tyre belts for heavy industrial vehicles.
• a radial tyre comprises a tread, two inextensible beads, two sidewalls connecting the beads to the tread, a carcass reinforcement and a belt placed circumferentially between the carcass reinforcement and the tread.
• the belt is made up of various rubber plies (or “layers") which may or may not be reinforced by reinforcing elements such as cabled threads or monofilaments, of the metal or textile type.
• the belt generally consists of several superposed belt plies, sometimes called “working” plies or “crossed” plies, the generally metallic reinforcing cables of which are placed so as to be practically parallel to one another within a ply but at an angle from one ply to another, that is to say they are inclined, whether symmetrically or not, to the median circumferential plane.
• These crossed plies are generally accompanied by various other auxiliary rubber plies or layers, which vary in width depending on the case and may or may not comprise metal reinforcing elements.
• such a tyre belt must meet various, often contradictory, requirements, in particular: it must be as rigid as possible at low deformation, as it contributes substantially to stiffening the tyre crown;
• the tyre belts for industrial vehicles comprise, as is known, one or more "protective" crown plies or layers located beneath the tread and covering the working crown ply or plies, which are designed to protect the rest of the belt from external attack, tearing or other perforations.
• multistrand cables especially multistrand cables having a single layer (i.e. with no central core of one or more other strands) of K x (L+M) construction, the K elementary strands of which are assembled, wound simultaneously in a helix as a single layer, with an assembly pitch PK.
• K x (L+M) construction the K elementary strands of which are assembled, wound simultaneously in a helix as a single layer, with an assembly pitch PK.
• Each of the K two-layer elementary strands, of L+M construction itself comprises a plurality of steel wires also wound together in a helix as two concentric layers (an inner layer of L wires and an outer layer of M wires).
• Such multistrand cables having a Kx(L+M) construction are well known and have been described in many patent documents, in particular for reinforcing protective crown plies of tyres for industrial vehicles such as heavy goods or civil engineering vehicles (see for example EP 1000074, US 6475636, US 7458200, WO 2004/003287 or US 2005/0183808, WO 2004/033789 or US 7089726 or else RD ⁇ Research Disclosure) No 33877, June 1992, 488-492.
• these multistrand cables must be impregnated as much as possible by the rubber in the tyre belts that they reinforce so that said rubber penetrates as much as possible into the spaces between the wires constituting the strands. If this penetration is insufficient, empty channels then remain along the strands, and corrosive agents, for example water, capable of penetrating the tyres, for example as a result of the tyre belt being cut or otherwise attacked, travel along these channels through said belt. The presence of this moisture plays an important role, causing corrosion and accelerating the fatigue process (so-called "fatigue-corrosion" effect) compared to use in a dry atmosphere.
• corrosive agents for example water
• One of the objectives of the present invention is to provide a multistrand steel cable having a high rupture strength and good elasticity, while still being easily penetrated by a rubber compound.
• a multistrand metal cable of 4x(4+M) construction which can especially be used for reinforcing tyre belts for industrial vehicles, formed from four elementary strands assembled in a helix with a helix pitch P3, each elementary strand consisting of a two-layer cable of 4+M construction comprising an inner layer C1 formed from four wires of diameter D1 , assembled in a helix with a pitch P1 , and an unsaturated outer layer C2 of M wires, M being greater than or equal to 8 and smaller than or equal to 1 1 , of diameter D2, these being assembled in a helix with a pitch P2 around the inner layer C1 , P1 being smaller than P2, the inner layer C1 and the outer layer C2 being wound in the same direction, and in which each of the diameters D1 and D2 is greater than or equal to 0.10 mm but less than or equal to 0.50 mm.
• the outer layer of each elementary strand is "unsaturated" in that the number M of wires of said outer layer C2 of the strand is smaller than the maximum number MMAX of wires of diameter D2 that can be wound in a helix, as a single layer, around the inner layer C1 of the strand.
• the invention also relates to the use of such multistrand cables for reinforcing rubber articles or semi-finished products, for example plies, hoses, belts, conveyor belts and tyres.
• the multistrand cable of the invention is particularly suitable for use as reinforcing element for a belt of a tyre designed for industrial vehicles, such as "heavy" vehicles, i.e. underground trains, buses, road transport vehicles (lorries, tractors, trailers), off-road vehicles, and agricultural or civil engineering machinery and other transport or handling vehicles.
• industrial vehicles such as "heavy" vehicles, i.e. underground trains, buses, road transport vehicles (lorries, tractors, trailers), off-road vehicles, and agricultural or civil engineering machinery and other transport or handling vehicles.
• the invention also relates to these rubber articles or semi-finished products themselves when they are reinforced with a multistrand cable according to an embodiment of the invention, particularly tyres designed especially for industrial vehicles.
• Figure 1 shows schematically, in cross section perpendicular to the axis of the cable, an example of a multistrand cable according to an embodiment of the invention, of 4x(4+8) cylindrical construction.
• Figure 2 shows schematically, in cross section perpendicular to the axis of the cable, an example of a multistrand cable according to an embodiment of the invention, of 4x(4+9) cylindrical construction.
• Figure 3 shows schematically, in cross section perpendicular to the axis of the cable, an example of a multistrand cable according to an embodiment of the invention, of 4x(4+10) cylindrical construction.
• Figure 4 shows schematically, in cross section perpendicular to the axis of the cable, an example of a multistrand cable according to an embodiment of the invention, of 4x(4+1 1 ) cylindrical construction.
• Figure 5 shows schematically an example of the twisting and in-situ rubber coating installation that can be used to produce strands for the manufacture of the multistrand cable of the invention.
• Figure 6 shows schematically, in radial section, a tyre for an industrial vehicle with a radial carcass reinforcement.
• This test enables the longitudinal air permeability of the tested metal cables to be determined by measuring the volume of air crossing through a sample under constant pressure over a given time.
• the principle of such a test is to demonstrate the effectiveness of the treatment of a cable in order to make it impermeable to air. The test has been described for example in the standard ASTM D2692-98.
• the test is carried out here either on multistrand cables as produced or on cables extracted from tyres or from the rubber plies that these multistrand cables reinforce, and therefore already coated with cured rubber.
• the metal cables In the first case (multistrand cables as produced), the metal cables must be coated beforehand from the outside with a rubber coating compound. To do this, a series of ten metal cables arranged so as to be in parallel (with an inter-strand distance of 20 mm) is placed between two skims (two rectangles measuring 80 x 200 mm) of a cured rubber composition, each skim having a thickness of 5.0 mm. The whole assembly is then clamped in a mould, each of the strands being maintained under sufficient tension (for example 3 daN) to ensure that it remains straight when being placed in the mould, using clamping modules.
• sufficient tension for example 3 daN
• the assembly is vulcanized (cured) over about ten to twelve hours at a temperature of about 120°C and under a pressure of 15 bar (rectangular piston measuring 80x200 mm), after which the assembly is unmoulded and cut up into 10 samples of metal cables thus coated, in the form of parallelepipeds measuring 10 mm x 10 mm x LT for characterization, LT being a predetermined length of metal cable.
• a conventional tyre rubber composition is used as rubber coating compound, said composition being based on natural (peptized) rubber and N330 carbon black (50 phr) and also containing the following usual additives: sulphur (7 phr), sulphonamide accelerator (1 phr), ZnO (8 phr), stearic acid (0.7 phr), antioxidant (1.5 phr) and cobalt naphthenate (1 .5 phr). Its Mooney viscosity at 100°C is equal to about 70, and its scorch time (T5) at 130°C is equal to about 10 min.
• Mooney viscosity measurement an oscillating viscosity meter as described in the French standard T43-005 (1991 ) is used according to the following principle: the composition in the green or uncured state (i.e. before curing) is moulded in a cylindrical enclosure heated to 100°C. After preheating for one minute, the rotor rotates within the sample at 2 rpm and the useful torque for sustaining this movement is measured after 4 minutes of rotation.
• the scorch time is measured at 130°C in accordance with the NF-T43-005 standard.
• the change in viscosity index as a function of time is used to determine the scorch time of a rubber composition, assessed in accordance with the aforementioned standard by the parameter T5, expressed in minutes, and defined as being the time needed to increase the viscosity index (expressed in Mooney units) by 5 units above the minimum value measured for this index.
• the test is carried out on a predetermined length LT of metal cable (for example equal to P3 or 6 cm), thus coated with its surrounding rubber composition (or rubber coating compound), in the following manner: air under a pressure of 1 bar is injected into the inlet of the strand and the volume of air leaving it is measured using a flow meter (calibrated for example from 0 to 500 cm 3 /min).
• a flow meter calibrbrated for example from 0 to 500 cm 3 /min.
• the strand sample is immobilized in a compressed seal (for example a rubber or dense foam seal) in such a way that only the amount of air passing through the metal cable from one end to the other, along its longitudinal axis, is measured.
• the sealing capability of the seal is checked beforehand using a solid rubber sample, that is to say one without a cable.
• the measured average air flow rate (the average over the 10 samples) is lower the higher the longitudinal impermeability of the metal cable. Since the measurement is accurate to ⁇ 0.2 cm 3 /min, measured values of 0.2 cm 3 /min or less are considered to be zero - they correspond to a strand that can be considered to be completely airtight along its axis (i.e. along its longitudinal direction).
• an "airtight" metal cable is characterized by an average air flow rate of 0.2 cm 3 /min or less, whereas a “practically airtight" metal cable is characterized by an average air flow rate of less than 2 cm 3 /min, preferably less than 1 cm 3 /min.
• any interval of values denoted by the expression "between a and b" represents the range of values going from more than a to less than b (i.e. the limits a and b are excluded) whereas any interval of values denoted by the expression “from a to b” means a range of values going from a up to b (i.e. the strict limits a and b are included).
• metal cable is understood by definition in the present application to mean a cable formed from wires consisting predominantly (i.e. more than 50% by number of these wires) or entirely (100% of the wires) of a metallic material.
• the wires are preferably made of steel, more preferably carbon steel. However, it is of course possible to use other steels, for example stainless steel, or other alloys.
• carbon steel When a carbon steel is used, its carbon content (percentage by weight of steel) is preferably between 0.2% and 1.2%, especially between 0.5% and 1 .1 %. These contents represent a good compromise between the mechanical properties required of the tyre and the feasibility of the wires. It should be noted that a carbon content between 0.5% and 0.6% makes such steels finally less expensive as they are easier to draw.
• Another advantageous embodiment of the invention may also consist, depending on the intended applications, in the use of steels having a low carbon content, for example between 0.2% and 0.5%, in particular because of a lower cost and greater wire drawability.
• the metal or steel used may itself be coated with a metal layer that improves, for example, the processing properties of the metal cable and/or its constituent components, or the usage properties of the cable and/or of the tyre themselves, such as the adhesion, corrosion resistance or aging resistance properties.
• the steel used is coated with a layer of brass (Zn-Cu alloy) or of zinc. It will be recalled that, during the wire manufacturing process, the brass or zinc coating makes wire drawing easier and makes the wire bond better to the rubber.
• the wires could be coated with a thin metal layer other than a brass or zinc layer, and/or with organic coupling agents possibly based on silanes, for example having the function of improving the corrosion resistance of these wires and/or their adhesion to rubber, for example a thin layer of Co, Ni, Al, or an alloy of two or more of the metals Cu, Zn, Al, Ni, Co, Sn.
• organic coupling agents possibly based on silanes, for example having the function of improving the corrosion resistance of these wires and/or their adhesion to rubber, for example a thin layer of Co, Ni, Al, or an alloy of two or more of the metals Cu, Zn, Al, Ni, Co, Sn.
• the strands used in the multistrand cable of the invention are preferably made of carbon steel and have a rupture strength (RM) of preferably greater than 2500 MPa, more preferably greater than 2800 MPa.
• RM rupture strength
• the total elongation at break (denoted by AT) of each constituent strand of the cable according to an embodiment of the invention, which is the sum of its structural elastic and plastic elongations, is preferably greater than 2.0%, more preferably at least 2.5%.
• the multistrand metal cable of the invention has a 4 x (4+M) construction. It comprises four elementary strands assembled in a helix with a helix pitch P3, each elementary strand consisting of a two-layer cable of 4+M construction comprising an inner layer C1 formed from four wires of diameter D1 , assembled in a helix with a pitch P1 , and an unsaturated outer layer C2 of M wires, M being greater than or equal to 8 and smaller than or equal to 1 1 , of diameter D2, these being assembled in a helix with a pitch P2 around the inner layer C1 , P1 being smaller than P2, the four wires of the inner layer C1 being wound in a helix in the same twist direction as the M wires of the outer layer C2, the M wires of the outer layer C2 being wound in the same direction as said four elementary strands assembled in a helix with a helix pitch P3.
• Each of the diameters D1 and D2 is greater than or equal to 0.10
• the pitch P represents the length measured parallel to the axis of the outer strand or of the multistrand cable, after which a wire or an outer strand having respectively this pitch makes one complete revolution about said axis.
• the outer layer of each elementary strand is "unsaturated" in that the number M of wires of said outer layer C2 of the strand is smaller than the maximum number MMAX of wires of diameter D2 that can be wound in a helix, as a single layer, around the inner layer C1 of the strand.
• M MMAX-1
• MMAX corresponds to the integer part of X.
• the average minimum distance between the wires of diameter D2 wound in a helix around the inner layer C1 of the strand is greater than or equal to D2/MMAX and more preferably still greater than or equal to 0.05 mm.
• each of the diameters D1 and D2 is greater than or equal to 0.15 mm but less than or equal to 0.35 mm.
• the pitch P1 is greater than or equal to 3 mm but less than the pitch P2, the pitch P2 being less than or equal to 20 mm (3 mm ⁇ P1 ⁇ P2 ⁇ 20 mm). More preferably, the pitch P2 is less than or equal to 15 mm (3 mm ⁇ P1 ⁇ P2 ⁇ 15 mm) and even more preferably less than or equal to 10 mm (3 mm ⁇ P1 ⁇ P2 ⁇ 10 mm).
• P2 is greater than or equal to 5 mm but less than or equal to 10 mm.
• the consequence of choosing these preferred values for the pitches P1 and P2 is that the wires of the outer layer C2 remain on the surface of the cylindrical envelope formed by the wires of the inner layer C1 . This increases the unsaturation of the outer layer C2 and consequently the penetrability of the strand.
• P3 is greater than or equal to 7 mm but less than or equal to 25 mm, and even more preferably greater than or equal to 10 mm but less than or equal to 20 mm.
• the consequence of these preferred values for the pitches P3, P2 and P1 and the choice of the same direction of twisting result in an addition of twists, which is advantageous.
• D1 8
• D1 may be equal to D2 or different from D2.
• the ratio D1/D2 of the diameters D1 and D2 is greater than or equal to 0.5 but less than or equal to 1.5, and even more preferably this ratio D1/D2 is greater than or equal to 0.7 but less than or equal to 1 .3.
• Figures 1 to 4 show schematically cables according to embodiments of the invention.
• Figure 1 shows schematically, in cross section perpendicular to the axis of the cable (assumed to be straight and at rest), an example of a multistrand cable 10 according to an embodiment of the invention, of 4x(4+8) construction.
• the diameter D1 of the wires 1 1 of the inner layer C1 is the same as the diameter D2 of the wires 12 of the outer layer C2.
• the value of MMAX is equal to 10.
• the average minimum distance between the wires 12 of the outer layer C2 is greater than or equal to D2/8 and corresponds to one of the criteria as defined above for the outer layer C2 to be unsaturated.
• Figure 2 shows schematically a second example of a multistrand cable 10 according to an embodiment of the invention, of 4x(4+9) construction.
• the diameter D1 of the wires 1 1 of the inner layer C1 is the same as the diameter D2 of the wires 12 of the outer layer C2.
• the value MMAX is equal to 10.
• the average minimum distance between the wires 12 of the outer layer C2 is greater than or equal to D2/9 and corresponds to one of the criteria as defined above for the outer layer C2 to be unsaturated.
• Figure 3 shows schematically a third example of a multistrand cable 10 according to an embodiment of the invention, of 4x(4+10) construction.
• the diameter D1 of the wires 1 1 of the inner layer C1 is greater than the diameter D2 of the wires 12 of the outer layer C2.
• the average minimum distance between the wires 12 of the outer layer C2 is greater than or equal to D2/10.
• Figure 4 shows schematically a final example of a multistrand cable 10 according to an embodiment of the invention, of 4x(4+1 1 ) construction.
• the diameter D1 of the wires 1 1 of the inner layer C1 is greater than the diameter D2 of the wires 12 of the outer layer C2.
• the average minimum distance between the wires 12 of the outer layer C2 is greater than or equal to D2/1 1 .
• an assembly step in which the four core wires are twisted or cabled in order to form the inner layer C1 of the strand at an assembly point; optionally, downstream of said point for assembling the four core wires, a coating step in which the inner layer C1 of the strand is coated with the uncured (i.e. uncrosslinked) filling rubber compound;
• a final step of equalizing torsions in particular during the coating operation.
• the wires undergo both a collective twist and an individual twist about their own axis, thereby generating an untwisting torque on each of the wires.
• One preferred feature of the above process is to use, when assembling both the inner layer (C1 ) of the strand and the outer layer C2 of the strand, a twisting step.
• the four core wires are twisted together (S or Z twist direction) in order to form the inner layer C1 of the strand, in a manner known per se; the wires are delivered by supply means, such as spools, a separating grid, whether or not coupled to an assembling guide, suitable for making the core wires converge at a common twisting point (or assembly point).
• supply means such as spools, a separating grid, whether or not coupled to an assembling guide, suitable for making the core wires converge at a common twisting point (or assembly point).
• the inner layer C1 of the strand thus formed may then be coated with uncured filling rubber compound, supplied by an extrusion screw at a suitable temperature.
• the filling rubber compound may thus be delivered to a single fixed small point, by means of a single extrusion head without having to individually coat the wires upstream of the assembly operations, before formation of the inner layer as described in the prior art.
• twist equalizing is understood here to mean, as is well known to those skilled in the art, the cancelling-out of the residual torsional moments (or of elastic return moments due to untwisting) acting upon each thread of the strand, both in the inner layer C1 of the strand and in the outer layer C2 of the strand.
• the manufacture of the outer strand is complete.
• This strand is wound up on one or more receiving spools, for storage, before the subsequent operation of cabling the elementary strands in order to obtain the multistrand cable of the invention.
• An assembling/rubber-coating device that can be used for implementing the process described above is a device comprising, from the upstream end to the downstream end, along the direction of advance of a strand being formed:
• FIG. 5 shows an example of a twisting assembly device 200 having a rotating feed and a rotating receiver, which can be used for the manufacture of a strand of the cylindrical layered type (wherein the pitch P1 of the layer C1 differs from the pitch P2 of the layer C2), for example of 4+8 construction as illustrated in Figure 1 .
• feed means 210 deliver four core wires 1 1 (only three of which are depicted) through a distributing grid 21 1 (an axis symmetric distributor), which may or may not be coupled to an assembling guide 212, beyond which the four wires 1 1 converge to an assembly point or twisting point 213, in order to form the inner layer (C1 ) of the strand.
• the inner layer C1 can then pass through an optional coating zone consisting, for example, of a single extrusion head 214 through which the inner layer is to pass.
• the distance between the point of convergence 213 and the coating point 214 is for example between 50 cm and 1 m.
• the N wires 12 of the outer layer (C2) of the strand, for example eight wires, delivered by feed means 220, are then assembled by being twisted around the optionally rubber-coated inner layer (C1 ) of the strand progressing along the direction indicated by the arrow.
• the strand C1 + C2 thus formed is finally collected on a rotating receiver 240 after having passed through the means 230 for equalizing torsions consisting for example of a straightener or twister- straightener.
• the process for manufacturing the multistrand cable of the invention is carried out, in a manner well known to those skilled in the art, by cabling or twisting the previously obtained elementary strands using cabling or twisting machines designed for assembling the strands.
• the twisting process used comprises the following known steps (see for example the aforementioned patent application WO 2004/003287) for obtaining a preferential multistrand cable of the HE (high elongation) type:
• the four elementary strands are wound together in a helix as a single layer, with a given transient twist pitch;
• an overtwist is applied so as to reduce this transient pitch, that is to say to increase the helix angle of said layer and, as a consequence, the helix curvature of the latter;
• the cable obtained is stabilized by untwisting it, so as to obtain a zero residual torque.
• the multistrand cable of the invention may be used for reinforcing articles other than tyres, for example hoses, belts, conveyor belts; advantageously, it could also be used for parts of a tyre other than its crown reinforcement, especially for the carcass reinforcement of tyres for industrial vehicles.
• the cable of the invention is particularly suitable as a tyre crown reinforcement for large industrial vehicles, such as civil engineering vehicles, especially of the mining type.
• Figure 6 shows very schematically a radial cross section through a tyre with a metal crown reinforcement, which may or may not be in accordance with the invention, in this general representation.
• This tyre 1 comprises a crown 2 reinforced by a crown reinforcement or belt 6, two sidewalls 3 and two beads 4, each of these beads 4 being reinforced by a bead wire 5.
• the crown 2 is surmounted by a tread.
• a carcass reinforcement 7 is wound around the two bead wires 5 in each bead 4, the turn-up 8 of this reinforcement 7 oriented for example towards the outside of the tyre 1, which Is shown here mounted on its rim 9.
• the carcass reinforcement 7 is formed by at least one ply reinforced by "radial" cables, that is to say these cables are practically parallel to one another and extend from one bead to the other so as to make an angle of between 80" and 90° with the median circumferential plane (i.e. the plane perpendicular to the rotation axis -of the tyre, which plane is located half-way between the two beads 4 and passes through the axial middle of the crown reinforcement 6).
• the tyre according to an embodiment of the invention is characterized in that its belt 6 comprises at least, as reinforcement for at least one of the belt plies, a multistrand cable according to an embodiment of the invention.
• this tyre 1 also includes, as is known, an inner layer of rubber compound or elastomer (usually called “inner liner") that defines the radially inner face of the tyre and is suitable for protecting the carcass ply from the diffusion of air coming from the space inside the tyre.
• inner liner an inner layer of rubber compound or elastomer
• the carbon steel wires were prepared in a Known manner, for example from wire stock (5 to 6 mm in diameter) hich was firstly work-hardened, by rolling and/or drawing, down to an intermediate diameter close to 1 mm.
• the steel used for the cable according to an embodiment of the invention was, for example, an NT (normal tensile) carbon steel, the carbon content of which being about 0.7% and the balance consisting of iron, manganese, silicon and usual inevitable impurities due to the steel manufacturing process.
• NT normal tensile
• the wires of intermediate diameter underwent a decreasing and/or pickling treatment before their subsequent conversion. After a brass coating had been deposited on these intermediate wires, what is called a "final" work-hardening operation was carried out on each wire (i.e. after the final patenting heat treatment), by cold-drawing it in a wet medium with a drawing lubricant for example in the form of an aqueous emulsion or dispersion.
• the steel wires thus drawn have the following diameters and mechanical properties:
• the letter “R” corresponds to a reference cable. To manufacture these cables, twisting assembly means were used.
• the term “AS” denotes here the "structural elongation" of the cable. The way in which this term is measured is well known to those skilled in the art and described, for example, in the document US 2009/294009 (cf. Figure 1 and the description relating thereto).
• Table 3 shows the results of the air permeability tests.
• the permeability is characterized both by an average air flow rate (an average over 10 measurements) and by NP0, i.e. the number of measurements corresponding to a zero air flow rate, NP0 being determined on the test sample.

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• 2010
  • 2010-04-28 FR FR1053248A patent/FR2959517B1/fr not_active Expired - Fee Related
• 2011
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  • 2011-04-21 EP EP11715559.8A patent/EP2563965B1/en active Active
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  • 2011-04-21 WO PCT/EP2011/056462 patent/WO2011134900A1/en active Application Filing
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